This presentation highlights the upgrading steps for improved traffic aggregation at the regional hub sites in order to optimize traffic backhauling to the network core. In addition, a reliable, passive access solution to cellular mobile traffic for a Quality of Service (QoS) monitoring and billing has been proposed.

1. Unified Backhaul Performance
Optimization
Upgrading Cellular Mobile Networks
Dr. Stanislav Milanovic
PhD in Computer Science and Engineering

2. Abstract
This presentation highlights the upgrading steps for
improved traffic aggregation at the regional hub sites in
order to optimize traffic backhauling to the network
core.
In addition, a reliable, passive access solution to cellular
mobile traffic for a Quality of Service (QoS) monitoring
and billing has been proposed.

3. The evolution of 3G radio technologies have dramatically
increased bandwidth delivery to the end user and at the same
time shifted the bandwidth bottleneck from the radio segment to
the cellular backhaul network.
To minimize both, Capital Expenditure (CapEx) and Operating
Expenditure (OpEx) of the cellular backhaul, mobile operators
have been seeking a unified backhaul solution that is
technology-agnostic and addresses cellular backhaul evolution
phases while maximizing the reuse of the existing backhaul
infrastructure (Figure 1).
Introduction

4. Figure 1. Cellular mobile backhaul network showing last and second-mile
connection and an optical SDH ring connection to the RNC and BSC.

5. Objective
A converged backhaul has been envisioned by employing
cellular backhaul switching technology for economically
managing backhaul network expenses during 3G evolution
while reusing the actual backhaul infrastructure. Cellular
backhaul switching is a sub-class of multi-service switching
(MSS), designed to address cellular backhaul evolution needs.
The following step was to provide the QoS management tool
and billing system access to the cellular mobile traffic in a
reliable, transparent and cost-effective manner.

6. Packet-based Aggregation
In order to deliver both 2G and 3G services, the operator decided to
deploy a packet-based aggregation solution based on ATM MSS
that reduced transmission expenses and opened up bottlenecks in
the microwave links (Figure 2). ATM switches were deployed over
a bundle of E1s (IMA group).
On the input side there are 6 E1 lines to carry 2G GSM traffic from
8 base stations. Another 6 E1s carry 3G UMTS traffic from 6 base
stations. The 6 GSM E1s are groomed and a circuit emulation
service is used to concentrate the traffic such that 4.5 E1s will
suffice. The 6 UMTS lines are concentrated into 2.5 E1s. As a
result, 7 E1s are required to connect the hub site to the core
network, which is a significant reduction from the original 12.

7. Figure 2. ATM MSS implementation

8. This solution, which is based on a standard ATM
multi-service switching enables the mixing of all traffic on
one IMA group with static partitioning between GSM and
UMTS. However, standard ATM MSS architecture is
limited by the fact that the output comprises dedicated
GSM and UMTS channels. These are entirely separate
networks that cannot be shared using a dynamic allocation
process.

9. Backhaul Optimization
The need to further improve network performance while cutting
down network expenses led to an alternative solution able to deliver
much higher network performance by adding the application-layer
cellular backhaul switches.
This eliminated idling and protocol inefficiencies by adaptation of
the actual information to Variable Bit Rate traffic flows. It
performed statistical multiplexing of all 2G and 3G traffic, obtaining
maximal statistical gain for maximum network efficiency, and
provided full flexibility for sharing network resources according to
actual 2G and 3G traffic demands (Figure 3).

10. Figure 3. Optimized Backhaul
The E1 lines have been further reduced to four from the
initial 12. In addition, the network is entirely and
dynamically shared between GSM and UMTS traffic.

11. Project Outcomes
The integration of cellular backhaul switching improved network
performance by maximizing network efficiency, providing full
network flexibility, and enabling real-time network resource
allocation based on support of QoS for multi-generational voice,
video, and data traffic.
The operator has the flexibility now to expand his customer base as
well as to introduce new 3G/4G services for his customers at his
own pace, while preserving his investment in the network.

12. QoS and Billing Access for Cellular Mobile Services
Critical issues to the success of cellular mobile services:
1. Maintaining a high level of QoS, and
2. accurately tracking and billing service usage.
Since wireless technologies move most of the traffic to IP, an IP
network monitoring access has been proposed for integration within
the core network infrastructure.
The best place in the switching infrastructure to tap the wireless
traffic would be at the links between the SGSN and the GGSN,
because it was the first place that traffic from all mobile devices had
been converted to IP (Figure 4).

13. Figure 4. Cellular mobile infrastructure with data monitoring switch for
monitoring access
Deployed monitoring solution in the core network cleanely isolated
the QoS monitoring tool and billing system from the service traffic,
ensuring that they would never interfere with the customer's service.

14. Conclusion
Implemented cellular backhaul switching has cut backhaul
requirements by a factor of three (from 12 E1s to 4 E1s) and has also
dynamically optimized the resources dedicated to 2G and 3G
services. The operator could expand his customer base as well as to
effectively introduce new 3G and 4G services for his customers.
Integrated monitoring access layer gave the monitoring tool layer,
which included the QoS and billing equipment, full visibility of the
cellular mobile traffic without any risk of it being negatively
impacted. It substantially reduced the complexity and risk of routing
the traffic to the QoS monitoring tool and billing system because it
did not rely on configuring switch Span ports that would otherwise
be necessary. It was cost-effective because monitoring tap ports
were much less expensive than switch Span ports.